An unemployed man accused of murdering his young girlfriend with a screwdriver was on Friday jailed for one year over a lesser assault charge after prosecutors found the woman’s death was caused by drugs she took.

The Fanling Court heard Chui Ching-lung, 42, and the victim Tse Mei-yan, 28, became lovers after she was discharged from a drug addiction treatment centre on February 13 last year.

The couple moved in together at Fu Heng Estate in Tai Po, but their relationship soon turned sour.

Just over a month later on March 16, Tse was found lying naked on Chui’s bed, with extensive bruises over her face and limbs, when police and ambulance officers arrived at the scene.

She was certified dead soon after arriving Alice Ho Miu Ling Nethersole Hospital in the same district.

Chui admitted upon inquiry that he had quarrelled with Tse earlier that day because he suspected her of having an affair.

He claimed the argument led to Tse assaulting him, so he picked up a screwdriver and a hairdryer to hit her face, which caused her to faint.

“She cheated on me, and even hit me,” Chui told police under caution. “I got so angry that I used a screwdriver and a hairdryer to hit her head. She fainted so I called police.”

In another interview he admitted to hitting Tse’s head with the screwdriver several times, but said the force was not that great.

The confession led to Chui being charged with one count of murder in March last year.

But prosecutors at Fanling Court on Friday lowered the charge to one of assault occasioning actual bodily harm, after the autopsy revealed Tse’s death was directly caused by her drug intoxication, complicated by her head injuries.